The long term goals of this proposal are to identify the active sites of the enterotoxins and exfoliative toxins of Staphylococcus aureus. The toxin molecules will be genetically altered by site-directed mutagenesis of cloned genes and transformed into selected staphylococcal strains for expression. The altered toxins will be tested in animal model systems for loss of biological activity and for the ability to elicit protective antibody. The cat/kitten system will be used to analyze the enterotoxins. Similar studies will be conducted with the exfoliative toxins and the new-born mouse model will be used for assay of biological activity. We will also examine various regions of both toxin types for major immunological epitopes and for mitogenic activity. Mitogenic activity will be assayed by lymphoblast transformation and immunogenicity will be assayed by conventional immunochemical methodology. Regions selected for mutagenesis will be chosen initially on the basis conserved sequence between the serologically diverse molecules. We also intend to characterize and study the mechanism of transmission of a potentially unique class of transposon elements that carry antibiotic resistance and enterotoxin genes. Lastly, we wish to study the transmembrane secretion of these toxins by continuing to analyze a number of secretion mutants we have isolated.